The subject invention relates to an apparatus for assembling a stack of alternating positive and negative plates which together form a cell for use in multi-celled lead acid storage batteries as generally employed for automotive industrial and commercial applications.
The construction of a lead acid storage battery is generally accomplished by the series assembly of a plurality of discrete cells formed within a battery case, each cell having a nominal voltage when charged, of about 2.0 volts. Each cell is constructed by combining a plurality of alternately arranged rectangular, relatively thin positive and negative plates to form a stack. As fabricated each of these plates has an upstanding lug and the plates are situated within the stack so that all of the positive plate lugs lie along one side and all of the negative plate lugs lie along the opposite side. As assembled, the stack has an insulating separator placed between the plates to prevent the positive and negative plates from shorting out after a subsequent charging step.
In the production of battery plates, as in the production of most high volume, mass produced items there is a tolerance level within which the plates must be produced in order to be acceptable. However, within this tolerance, it is possible that there is a substantial variability both among the plates used within any given stack to form a cell and between the plurality of stacks which are assembled to form a battery. In the production of the battery, it would be highly advantageous if this variability could be accommodated and operated on in a single cycle of the production equipment used. This is especially critical at the processing stage where the positive lugs and the negative lugs within a cell have a commoning strap cast on them prior to the placement of the intercell connectors for the series assembly step.
One apparatus widely used for accomplishing task of commoning the battery lugs within each stack is the Farmer Cast-On-Strap (COS) machine. The Farmer Apparatus is adapted to produce, in a single cycle, a plurality of final assembled stacks sufficient to assemble one battery. The strap casting operation is done within the Farmer apparatus by holding the stacks with a device commonly referred to as a basket while the straps are cast onto the lugs. An example of a basket used with such apparatus is shown in prior art FIG. 1.
Referring now to FIG. 1, we see an isometric view of the Farmer Basket 10. As shown, is a boxlike structure comprising a square-cornered open frame 12 having sidewalls 14 and 16 and a front wall 18 which is square with both of the sidewalls. Further connected to the inner portion of the sidewalls is a plurality of fixed, regularly spaced divider plates 20 which are parallel to front wall 18 and act to form a series of internal cavities 22 within the area defined by frame 12. Frame 12 has no bottom per se but is adapted to fit on a mounting plate (not shown) which is a part of the Farmer Machine. When so mounted, Basket 10 can accommodate plates in either the lugs up or lugs down position.
Slidingly mated to the sides of Frame 12 is a compression frame 24. As shown, this comprises a square-cornered yoke fitted around and over end wall 18 and having a pair of side panels 26 and 28 which lie along the outer portion of sidewalls 14 and 16 and an end panel 30 which fits over and closes off the open end of Frame 12 to form the rearmost cavity 22 within frame 12. Connected to the top and bottom edges of side panels 26 and 28 by lugs 29 and parallel with end panel 30, is a plurality of clamping plates 32 which are disposed so that one of them lies and is reciprocally movable back and forth within each of cavities 22. As configured the compression plates are normally biased to be in a closed position which places them adjacent to the front divider plate of the cavity in which it is placed.
Further connected to compression frame 24 is handle 34 which is attached to the side panels by bolting, riveting or any other suitable means of attachment to form a yoke around frame 12. Machined into both side panels is a pair of horizontal slots 36 through each of which a lug 38 is mounted onto the sidewall. Connected between these lugs on the outersides of each side panel is one of a pair of extension springs 40 which create the compressive force which biases the compression plates to stay in a closed position.
When it is desired to insert a set of plate stacks into the basket, the Farmer machine clamps frontwall 18 and pushes out on handle 34 so that the basket frame 12 and compression frame 24 start to slide past each other as they are forced to part. In so doing, clamp plates 32 are pushed back from their normal closed position against the divider plates 20 to create a plurality of secondary rectilinear spaces 42 between the separated movable clamping plates 32 and the front stationary divider plate 20 in each of cavities 22. At the same time, the forwardmost ends of the slots 36 bear on lugs 38 which stretches the extension springs 40 and places them in tension. When the Farmer Machine stops pushing, the spaces 42 are open to a point where they are oversize relative to the plate stacks 44, which allows said stacks to be easily inserted therein by the machine operator. When the requisite number of stacks have been inserted into the opened spaces the Farmer Machine releases the pushing force at which time, the two extension springs 40 contract and attempt to return the two sliding sections back to the normal closed position. This return motion continues until one of the clamping plates 32 makes contact with the thickest of the battery stacks 44 within basket 10. Since all of the compression plates must move in and out as a unit, this return motion will therefore stop as soon as the first contact is made with that stack. Should it be noticeably thicker than one or more of the other stacks in the assembly, a problem arises with the thinner stacks not being as tightly clamped as the remainder. Consequently, when the basket moved to further process steps in the battery assembly line, it is quite possible that one or more of these thinner stacks will wobble to produce defective straps or even fall out of the basket. When this happens it is necessary that the system be stopped while the stack is replaced or a substitute, more evenly compressed basket is put in that position. The economics of the production line dictate that such events happen as infrequently as possible.
It is this problem which the preferred embodiment of the subject invention is intended to address. The instant invention is an improved basket device for use in an apparatus such as the Farmer COS Machine. The purpose of this basket device is to secure and move an assembly of stacks regardless of the variability in their composite thickness through the processing steps needed to common the cells used to form a finished battery.